Callback Commands

• Jan 11, 2024
• 6 minutes to read

The Scheduler callback command is the basic object which provides interaction between a Web client instance of the ASPxScheduler and its server part. When a specific task should be accomplished, the client control performs a callback to the server. A command, which forms the essential part of the callback, is then executed on the server and in the final stage of a callback, the client control is updated.

SchedulerCallbackCommand Class

There are numerous classes implemented to represent commands which serve to accomplish different tasks. They all have a common ancestor - the SchedulerCallbackCommand abstract class. It defines the following essential properties and methods:

string Id property

Gets or sets a string which uniquely identifies a command.

bool RequiresControlHierarchy property

Set it to true if a call to EnsureChildControls() method is required to ask the engine to populate the controls collection first before processing.

void Execute(string parameters) method

Executes a command. It processes the parameter information via the call to ParseParameters method, then checks the result of CanContinueExecute method, and if it is true, calls the ExecuteCore method. The FinalizeExecute method completes the execution. All mentioned methods are defined as virtual, so you can override them when necessary in command class descendants.

Usage

In JavaScript, you should use the control.RaiseCallback() method to invoke a callback command. The method’s argument specifies the command and passed parameters. It is a DevExpress.Web.ASPxScheduler.Internal.CallbackCommandInfo object which is represented by a string in the following format :

<command identifier>|<comma delimited parameters>

Refer to the following table which lists generally used commands, their identifiers and parameters:

Command identifier	SchedulerCallbackCommandId property	Description	Parameters
APTCANCEL	AppointmentCancel	Close the appointment editing form.	-
APTDATA	AppointmentData	Retrieves the specified appointment properties.	The client appointment id and a list of appointment properties to retrieve.
APTDATAEX	AppointmentDataEx	Performs a callback to retrieve appointment properties and, after that, executes a specified procedure.	A refresh action id, the client appointment id and a list of properties to retrieve.
APTDEL	AppointmentDelete	Delete the appointment edited in the appointment editing form.	-
APTSAVE	AppointmentSave	Save the appointment edited in the appointment editing form.	-
DLTAPT	ClientSideDeleteAppointment	Deletes the selected appointment.	-
EDTFRMSHOW	AppointmentFormShow	Show appointment editing form for the appointment with the specified client id.	Appointment client identifier (ASPxClientScheduler.GetSelectedAppointmentIds).
EDTFRMSHOWSID	ShowAppointmentFormByServerId	Show appointment editing form for the appointment with the specified server id.	Appointment identifier (ASPxSchedulerStorage.GetAppointmentId).
GOTODATE	GotoDate	Set the ASPxScheduler.Start property of the control to the specified datetime.	The number of seconds since 01/01/1970.
GOTODATEFORM	GotoDateForm	Invoke the GotoDate form.	-
GOTODAY	GotoToday	Set the ASPxScheduler.Start property of the control to the current client date.	-
INPLACEFORM	InplaceEditorEditForm	Invoke the appointment editing form for the appointment currently edited via the inplace editing form.	-
INPLACESAVE	InplaceEditorSave	Save the appointment edited via the inplace editing form.	-
INPLACESHOW	InplaceEditorShow	Invoke the inplace editor for the currently selected appointment.	-
INSRTAPT	ClientSideInsertAppointment	Inserts an appointment into a storage collection.	A list of property-value pairs for the new appointment.
REFRESH	Refresh	Perform an empty callback to reload a page.	-
SAVT	SwitchView	Switch the View.	SchedulerViewType
SVGT	SwitchGroupType	Switch the group type.	SchedulerGroupType
TZI	ChangeTimeZone	Set the ASPxScheduler client time zone.	A string, the time zone identifier which is valid for the System.TimeZoneInfo.Id property.
UPDTAPT	ClientSideUpdateAppointment	Updates selected appointment property values.	A list of property-value pairs.

When customizing the appointment editing form, you can insert your own JavaScript to perform specific tasks. The following code snippet illustrates the use of a client’s button click event to display a custom message, save appointment information and close the form.

<dx:ASPxButton runat="server" ID="btnOk" Text="OK" UseSubmitBehavior="False" AutoPostBack="False"
    EnableViewState="False" Width="91px" >
    <ClientSideEvents Click="function(s, e) {Thanks(s, e);}" />
</dx:ASPxButton>

function Thanks(s, e){
    alert('Thanks for saving!');
    scheduler.RaiseCallback('APTSAVE|');
    scheduler.RaiseCallback('APTCANCEL|');
}

Menu

A callback command may originate from a popup menu invoked from the scheduler’s View area or an appointment’s area. The menu to which a command belongs is indicated by a special prefix - MNUVIEW or MNUAPT respectively. This prefix is appended before the command identifier. You can send callback commands corresponding to menu items by specifying a proper prefix and a command’s name, equal to the SchedulerMenuItemId member.

To show a new appointment form, you can call the clientScheduler.RaiseCallback("MNUVIEW|NewAppointment") method. In order to edit an existing appointment, use the clientScheduler.RaiseCallback("MNUAPT|OpenAppointment") method.

When implementing your own menu commands, you should inherit them from the MenuAppointmentCallbackCommand base class instead of the SchedulerCallbackCommand class, as illustrated in the following code snippet:

C#

// CustomMenuAppointmentCallbackCommand
public class CustomMenuAppointmentCallbackCommand : MenuAppointmentCallbackCommand {
    string menuItemId = String.Empty;

    public CustomMenuAppointmentCallbackCommand(ASPxScheduler control) : base(control) { }

    public override string Id { get { return "USRAPTMENU"; } }
    public string MenuItemId { get { return menuItemId; } }

    protected override void ParseParameters(string parameters) {
        this.menuItemId = parameters;
        base.ParseParameters(parameters);
    }

    protected override void ExecuteCore() {
        Appointment apt = Control.SelectedAppointments[0];
        if (MenuItemId == "DeleteAppointment") {
            apt.Delete();
            return;
        }
        else if (MenuItemId == "BringMeCoffee") {
            // TODO: Add Code here
            return;
        }

        base.ExecuteCore();

    }
}

VB.NET

' CustomMenuAppointmentCallbackCommand
Public Class CustomMenuAppointmentCallbackCommand
    Inherits MenuAppointmentCallbackCommand
    Private menuItemId_Renamed As String = String.Empty

    Public Sub New(ByVal control As ASPxScheduler)
        MyBase.New(control)
    End Sub

    Public Overrides ReadOnly Property Id() As String
        Get
            Return "USRAPTMENU"
        End Get
    End Property
    Public ReadOnly Property MenuItemId() As String
        Get
            Return menuItemId_Renamed
        End Get
    End Property

    Protected Overrides Sub ParseParameters(ByVal parameters As String)
        Me.menuItemId_Renamed = parameters
        MyBase.ParseParameters(parameters)
    End Sub

    Protected Overrides Sub ExecuteCore()
        Dim apt As Appointment = Control.SelectedAppointments(0)
        If MenuItemId = "DeleteAppointment" Then
            apt.Delete()
            Return
        ElseIf MenuItemId = "BringMeCoffee" Then
            ' TODO: Add Code here
            Return
        End If

        MyBase.ExecuteCore()

    End Sub
End Class

Callback Interception

Use the BeforeExecuteCallbackCommand event to intercept a callback command. You can then analyze the CommandId parameter, and substitute a command if necessary.

The following code sample enables you to use your custom save procedure for the custom appointment editing form, and processes a custom callback command identifier, so it results in a proper command being executed.

C#

protected void ASPxScheduler1_BeforeExecuteCallbackCommand(object sender, 
        SchedulerCallbackCommandEventArgs e) {
    if (e.CommandId == SchedulerCallbackCommandId.AppointmentSave)
        e.Command = new MyAppointmentSaveCallbackCommand((ASPxScheduler)sender);
    else if (e.CommandId == "CREATVSPECAPT")
        e.Command = new CreateVerySpecialAppointmentCallbackCommand(
            (ASPxScheduler)sender);
    else if (e.CommandId == "MNUVIEW")
        e.Command = new CustomMenuViewCallbackCommand((ASPxScheduler)sender);
    else if (e.CommandId == "MNUAPT")
        e.Command = new CustomMenuAppointmentCallbackCommand((ASPxScheduler)sender);
}

VB.NET

Protected Sub ASPxScheduler1_BeforeExecuteCallbackCommand(ByVal sender As Object,  _
        ByVal e As SchedulerCallbackCommandEventArgs)
    If e.CommandId = SchedulerCallbackCommandId.AppointmentSave Then
        e.Command = New MyAppointmentSaveCallbackCommand(CType(sender, ASPxScheduler))
    ElseIf e.CommandId = "CREATVSPECAPT" Then
        e.Command = New CreateVerySpecialAppointmentCallbackCommand( _
            CType(sender, ASPxScheduler))
    ElseIf e.CommandId = "MNUVIEW" Then
        e.Command = New CustomMenuViewCallbackCommand(CType(sender, ASPxScheduler))
    ElseIf e.CommandId = "MNUAPT" Then
        e.Command = New CustomMenuAppointmentCallbackCommand( _
            CType(sender, ASPxScheduler))
    End If
End Sub